Validation of a Wearable Sensor Prototype for Measuring Heart Rate to Prescribe Physical Activity: Cross-Sectional Exploratory Study.

Background: Wearable sensors are rapidly evolving, particularly in health care, due to their ability to facilitate continuous or on-demand physiological monitoring.

Objective: This study aimed to design and validate a wearable sensor prototype incorporating photoplethysmography (PPG) and long-range wide area network technology for heart rate (HR) measurement during a functional test.

Methods: We conducted a transversal exploratory study involving 20 healthy participants aged between 20 and 30 years without contraindications for physical exercise. Initially, our laboratory developed a pulse wearable sensor prototype for HR monitoring. Following this, the participants were instructed to perform the Incremental Shuttle Walk Test while wearing the Polar H10 HR chest strap sensor (the reference for HR measurement) and the wearable sensor. This test allowed for real-time comparison of HR responses between the 2 devices. Agreement between these measurements was determined using the intraclass correlation coefficient (ICC) and Lin concordance correlation coefficient. The mean absolute percentage error was calculated to evaluate reliability or validity. Cohen d was used to calculate the agreement's effect size.

Results: The mean differences between the Polar H10 and the wearable sensor during the test were -2.6 (95% CI -3.5 to -1.8) for rest HR, -4.1 (95% CI -5.3 to -3) for maximum HR, -2.4 (95% CI -3.5 to -1.4) for mean test HR, and -2.5 (95% CI -3.6 to -1.5) for mean recovery HR. The mean absolute percentage errors were -3% for rest HR, -2.2% for maximum HR, -1.8% for mean test HR, and -1.6% for recovery HR. Excellent agreement was observed between the Polar H10 and the wearable sensor for rest HR (ICC=0.96), mean test HR (ICC=0.92), and mean recovery HR (ICC=0.96). The agreement for maximum HR (ICC=0.78) was considered good. By the Lin concordance correlation coefficient, the agreement was found to be substantial for rest HR (r=0.96) and recovery HR (r=0.96), moderate for mean test HR (r=0.92), and poor for maximum HR (r=0.78). The power of agreement between the Polar H10 and the wearable sensor prototype was large for baseline HR (Cohen d=0.97), maximum HR (Cohen d=1.18), and mean recovery HR (Cohen d=0.8) and medium for mean test HR (Cohen d= 0.76).

Conclusions: The pulse-wearable sensor prototype tested in this study proves to be a valid tool for monitoring HR at rest, during functional tests, and during recovery compared with the Polar H10 reference device used in the laboratory setting.